U.S. Pat. No. 5,540,495 (Pickel) discloses an extruder screw drive has a first and a second motor, a screw mechanism connected to the first motor and to the extruder screw for translating it in the extrusion cylinder, and a slide mechanism connected to the second motor and to the extruder screw for rotating it in the extrusion cylinder. The screw mechanism and the slide mechanism are coaxial and partially fit into one another to provide an axially compact arrangement. The motors can be hollow shaft electric motors axially aligned together, and pressure regulated hydraulic axial force can be added to the extruder screw during plasticating as it retracts due to increased volume of plastic at an output end of the extrusion cylinder.
U.S. Pat. No. 7,390,185 (Teng et al.) discloses a drive unit operable to translate and rotate a shaft, the drive unit including: (i) a hollow electric motor having a rotor, (ii) a fluid cylinder, (iii) means for connecting the shaft to the rotor of the hollow electric motor, (iv) means permitting the shaft to move lengthwise coupled with the fluid cylinder, and (iv) means connecting the fluid cylinder to the shaft, whereby the shaft may be rotated by the hollow electric motor and moved lengthwise by the fluid cylinder, and wherein the fluid cylinder has an outer wall coupled with the rotor of the hollow electric motor.
Great Britain Pat. No. 1,094,037 (Zdarske) discloses an axially reciprocable injection screw connected to a cylinder which co-operates with a fixed piston and is rotatable by a drive motor which is axially fixed with respect to the movable cylinder. The drive motor may be an electric motor or an hydraulic motor comprising a rotor and stator. The screw is advanced axially by fluid pressure introduced between the piston and cylinder through a pipe. By unscrewing plugs in the cylinder and piston respectively the screw can be withdrawn for servicing.